The present invention relates to disk cartridges that can accommodate a disk serving as a recording media and expose it by opening a pair of shutter members.
Disk-shaped recording media are exemplified by write-once or rewritable optical disks for recording and playback of information such as audio data, video data, and computer data and playback-only optical disks. Such optical disks are rotatably accommodated in cartridge cases because the adhesion of foreign matter such as dust and fingerprints to a signal recording surface impairs reliable recording and playback of data. A typical disk cartridge includes, for example, a cartridge case rotatably accommodating an optical disk and having an opening for recording and/or playback which is closed by shutter members. These shutter members move and open the opening only when the disk cartridge is inserted into a recording and/or playback device.
Referring to FIGS. 25 and 26, a disk cartridge 201 as disclosed in Japanese Unexamined Patent Application Publication Nos. 2001-332054 and 2002-50147, for example, includes a cartridge case 202 including an upper shell 202a, a lower shell 202b coupled thereto, an inner rotor 204 rotatably holding an optical disk 203 in the cartridge case 202, an opening 206 provided in the lower shell 202b of the cartridge case 202, and a pair of shutter members 205a and 205b that are opened to expose the optical disk 203 through the opening 206 in recording and/or playback. As the inner rotor 204 is rotated in one direction in the cartridge case 202 of the disk cartridge 201, the shutter members 205a and 205b move and close the opening 206 of the lower shell 7 to protect the optical disk 203. As the inner rotor 204 is rotated in the opposite direction, the shutter members 205a and 205b move and open the opening 206 to expose the optical disk 203 through the opening 206 for recording and/or playback.
FIG. 27 illustrates the relative positions of the upper shell 202a, the lower shell 202b, the inner rotor 204, and the optical disk 203. The upper shell 202a has a substantially rectangular main surface portion, an outer circumferential wall 211 on the periphery of the main surface portion, an inner circumferential wall 212 inside the outer circumferential wall 211, and a guide groove 213 for guiding the inner rotor 204 between the circumferential walls 211 and 212. The main surface portion has a substantially arc-shaped front end which is inserted into a recording/playback device. The lower shell 202b, which is coupled to the upper shell 202a, has a substantially rectangular main surface portion and an outer circumferential wall 214 on the periphery of the main surface portion. The main surface portion has a substantially arc-shaped front end which is inserted into a recording/playback device. The inner rotor 204 has a substantially circular main surface portion 215 and an annular portion 216 disposed on the periphery thereof. The main surface portion 215 and the annular portion 216 form a space for accommodating the optical disk 203.
The upper shell 202a and the lower shell 202b are coupled with the outer circumferential walls 211 and 214 butting against each other. The inner rotor 204 is rotatably disposed inside the outer circumferential wall 214 of the lower shell 7 such that the leading end of the annular portion 216 engages with the guide groove 213 of the upper shell 202a. The inner circumferential wall 212 of the upper shell 202a is positioned inside the annular portion 216 so as to surround the space accommodating the optical disk 203. The inner circumferential wall 212 has such a height that a predetermined gap 217 is left between the leading end of the inner circumferential wall 11 and the main surface portion of the inner rotor 204. The gap 217 ensures that the inner circumferential wall 212 does not come into contact with the inner rotor 204 or interfere with the rotation thereof.
Referring to FIG. 28, a large impact resulting when, for example, the disk cartridge 201 is accidentally dropped may bend the upper shell 202a and the lower shell 202b and thus deform the space accommodating the inner rotor 204 in the cartridge case 202. If such deformation widens the gap 217 to larger than the thickness of the optical disk 203, the rim of the optical disk 203 may squeeze between the leading end of the inner circumferential wall 212 and the main surface portion 215 of the inner rotor 204.
If the rim of the optical disk 203 squeezes into the gap 217, the inner rotor 204 is, for example, pressed against the lower shell 202b and thus no longer rotates. As a result, the pair of shutter members 205a and 205b, which rotate as the inner rotor 204 rotates, pose difficulty in opening the opening 206 for the recording or playback of the optical disk 203. In addition, the inner rotor 204 pressed against the lower shell 202b deforms the lower shell 202b and causes a gap between the lower shell 202b and the shutter members 205a and 205b around the opening 206. This gap promotes the intrusion of foreign matter such as dust into the cartridge case 202 and results in damage to the optical disk 203.
The optical disk 203, on which information signals are densely recorded, have fine spots formed by focusing a short-wavelength light beam using an objective lens with high numerical aperture in close proximity to the optical disk 203. If, for example, the disk cartridge 201 deforms and causes a gap between the inner rotor 204 and the shutter members 205a and 205b, foreign matter such as dust can intrude into the cartridge case 202 and adhere to the optical disk 203. Such foreign matter may obstruct accurate recording/playback of information signals and contaminate the optical disk 203 and the objective lens.